1. Field of the Invention
This invention relates generally to in-line total-flow meters for liquids. More particularly, it relates to apparatus for use in rapidly and precisely metering the average rate of flow of a liquid in a conduit. As used herein, the term "liquid" includes single-component liquid systems, liquid solutions, liquids containing particles and/or gas bubbles, and the like.
2. Problem
This invention was made in response to a need for improved apparatus for periodically determining the rate of flow of an aqueous liquid through a conduit. The liquid was hot, corrosive, and electrically conductive; it contained entrained gas in the form of many tiny bubbles. The primary reasons for making the determination were to establish whether the flow through the conduit was at design value and, if not, to measure the deviation from that value and take corrective action. Previously, the flow rate of the liquid has been measured by valving the flow from the conduit into a calibrated volume, determining with a stopwatch the time required to fill the volume, and then calculating the corresponding average flow rate. That procedure was subject to serious disadvantages, including the following: (1) Diverting the liquid as described changed the upstream flow conditions, thus altering the flow rate under measurement. (2) The diverted liquid could not be returned to the conduit for use but instead had to be discarded as waste. (3) Diversion of the liquid from the conduit was potentially hazardous. As an alternative, various commercial flowmeters were tested as means for measuring the flow rate of the liquid, but none was entirely satisfactory. The most suitable of these, a magnetic flowmeter, did not perform satisfactorily because of the bubbles of gas in the liquid. The provision of debubbler did not improve operation of the flowmeter appreciably.